thoughts on water sensing needs of non-profits in Louisiana
I don't have experience building a probe, but i have a lot of
experience using hydrolab and YSI devices in ways that are not
We have a need to monitor oxygen demand independently of the paper
mills, who monitor their own waste for DEQ in DMRs. DEQ has little to
no response capacity, so it's these recurrent industrial catastrophes
are when we need to monitor the river, and able to do it quickly. it
would be appropriate to drop sensors with loggers, rather than boat
around spot checking with handhelds, which is cheaper from an
equipment point of view but bleeds away gas and limited staff time.
an oxygen sensor is calibrated based on temp and conductivity; and
conductivity gives you one way of measuring salinity
so, commonly, handheld field probes (like YSI 85) have temp, salinity,
conductivity, and oxygen. YSI 85 is a standard scientific probe for
These are also common pollutants of concern. ranked by priority::
nitrate / ammonia
enterococcus / e coli
PAHs and phenols from oil waste and paper mill effluent (also strange
organic chemicals like Sylvic acid)
Mg, Ar, Cu, Pb, other metals
Salt ::brine from old drilling muds from re-mobilized oil waste pits
I'm glad you're focusing on an oxygen sensor. Whether we're fighting
faulty water treatment or monitoring paper mill effluent, oxygen is
often something we, as watchdogs, want to measure. unfortunately it's
very variable, and we often are not in the right place at the correct
often we can't measure or can't make sense of spot measurements. DEQ
can't, either. many person hours and fuel were burned in monitoring
oxygen on the river in response to recent fish kill in Bogalusa, for
example, because the agency uses a handheld probe and runs up and down
the river in a boat taking readings.
example reports (without time of day) are here.
But what we really want to get is repeated measures of early-morning
DO at depth over a series of days. knowing the daily variation is
also useful. DEQ does not wake up early, and neither do we, honestly.
a logger would be best, a cheap logger would be excellent.
fisheries research depends on repeated spot measurements over years to
get a picture of the oxygen conditions on the river.
the agency also does not take readings at high water, due to safety
precautions. and yet, there are a certain types of toxins (like
sylvic acid from paper mills) that are activated only during high
water that mobilizes bottom sediments. so if something nasty in
sediments gets re-mobilized from the river bed during high water, we
don't see it or any local effects.
there are similar problems downstream of watertreatment ponds; the
problems are more chronic--as the ponds age, they fill and become
useless. but our sampling challenges are similar.
A non-profit that would want to collect data would need to do so with
less money and staff. rather than running two boat trips on 40 river
miles a day for 6 locations ("stations"), it would be cheaper to drop
six probes in place for a couple of days at a time, and just data
collection / battery recharge boat runs on volunteer time. from
experience with stream loggers in Georgia, i wouldn't want to leave
probes out for long periods. probes are tampered with or are more
likely to be displaced by multiple high water events. so the time
period is similar to a fishing rig. also, probes that sit for a while
get gunked up, this is the problem with the water quality stations in
city park. algae.
it would be excellent to have droppable oxygen probes, weighted to the
bottom of the river, buoyed for placement in the water column, but
secured to the bank by a second line. attached is a dream diagram.
the bottom probe is priority; having multiple drop stations makes the
equipment cost ring up quickly, one bottom probe is enough, really.
deployment is crucial in these crises, where it takes DEQ weeks to
respond to a problem. But we could also use a similar protocol to get
a weekly profile during "typical" seasons / high water periods, to
establish a record of what the river should be, so we can track long
problem: stable oxygen probes require water agitators, like the one
on the hydrolab multi-probe. If the current is quick enough (1 foot
per sec), it ceases to be a problem, but periods of slack water are
the times when oxygen will be low, which is the event we want to
capture and know the frequency of.
another problem would be calibrating the probes, which would eat up a
lot of time before deployment, compared to handhelds. still, it seems
worth it, given the time saved not running up and down the river over
Again, i don't know if this is the information you were looking for;
It applies to the electric/ membrane style of oxygen sensor that i am
familiar with, and is relevant to common dilemmas I face as part of
community-based organizations trying to learn about our rivers,
protect and improve them.
proprietary equipment i have used (besides YSI)
Hydrolab multi-probe Sondes
neat optical data transfer units
cheap underwater sensors
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